Car use forecasts put quality up in the air

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A report used to justify plans for 160,000 homes in new-release areas claims that Sydney's air quality will deteriorate only slightly, but it relies on the most optimistic of assumptions about getting people out of their cars.

It depends not only on the growth in car use slowing sharply but also on the construction of three railways so they are running by 2016.

The air modelling study by the Department of Environment relies on car use growing in line with population growth, even though for the past decade it has consistently run well above this rate. Cars are the main source of pollution in Sydney.

Planning ministers have said publicly the study shows that the Bringelly area - which was rejected for housing in the 1980s because of fears about air quality - was now suitable because of improvements in emission controls.

But the air quality study has never been made public.

The Herald has obtained the report under freedom of information laws. It shows that while Sydney has quite good air quality by world standards, it continues to exceed the National Environment Protection Measures on two measures: the amount of ozone in the air and the amount of fine particles, mainly from diesel. The study found that these would worsen slightly over the next two decades. Ozone has been linked with asthma, respiratory illness and impaired lung function after long-term exposure.

The topography of the basin means air quality is consistently worse in western Sydney. Emissions are blown by the predominantly north-easterly winds into the west and on the way are chemically altered by the sun, producing ozone. They then settle overnight in the low-lying areas around the Hawkesbury and Nepean rivers and around Bringelly. This is why the Greiner government abandoned its plan for a mini-city at Bringelly, a plan the Carr Government has revived.

As departmental documents and the air quality report itself note, the relatively positive forecasts for 2016 and 2026 depend on assumptions provided by the Department of Infrastructure - assumptions about population growth, vehicle use, emission standards for cars and trucks, and the growth of polluting industries.

"The modelling results are dependent on the scenario design and the assumptions used to derive the scenario … If the figures for population growth, transport

infrastructure provision, levels of employment containment, land use and resultant vehicle use provided by [the Department of Planning] are not valid, an increase in population and associated emissions could lead to a worsening air quality in Sydney," one environment officer, Suzanne Quigley, said in an email to her superiors.

Between 1991 and 2001 growth in car use, measured by vehicle kilometres travelled, has been an average 2.3 per cent a year, while population growth has averaged 1.3 per cent a year. Growth on the urban fringe has been even higher.

The acting director of Sydney Planning in the Department of Environment, Gillian Grenfell, also cast doubt on the validity of the modelling results in correspondence. "The results of the modelling undertaken may not apply to the new Metropolitan Strategy," she wrote.

While the State Government's Metropolitan Strategy aims to attract jobs to western Sydney, close to the new-release areas for homes, and to create "walkable neighbourhoods", it does not envisage building the rail line to the city's south-west until 2019.

No date has been set for the north-west line.

The Planning Department told the Herald: "For modelling purposes it was assumed that rail links were provided to the north-west and south-west sectors, the Parramatta rail link was built, and that the three western Sydney transit ways were built and operational. It was also assumed that the road network would continue to develop at existing rates."

The report assumes that Australia implements world's best practice on vehicle emissions controls by introducing the Euro IV and V standards by 2010. This is being considered by the Federal Government.

The report gives some idea of what may happen if the assumptions are wrong. The department ran some sensitivity modelling, where it assumed emissions standards did not improve and Sydney's population still grew. This modelling showed that the days on which the ozone standard was breached could rise by as much as 25 per cent.